Illegal Moves

Illegal moves can occur in chess in many ways. The simplest way is for a beginner to move a piece improperly. Knights sometimes move 2-2 (diagonally) instead of L-shaped moves. Diagonal bishop and Queen moves sometimes stray onto an adjacent square of a different color.

The most common cause of illegal moves in junior tournaments is probably check. The kids just don’t see check of the King. They don’t see that their opponent has checked their King. They don’t even see that they’ve checked the enemy King. And they move pinned pieces exposing the King. Sometimes both Kings are in check at the same time and neither player sees it!

Other illegal moves arise from violations of other complex chess rules. For example, the castling rules may be violated by castling out of check, castling through check, etc.

In most tournaments, an illegal move should be undone and a new legal move should be played instead. This means that the game should continue by “fixing” an illegal move sequence.

Some tournaments adopt a “two illegal move forfeit” rule. This means that if you play an illegal move twice, the second time you lose the game by forfeit. Some tournaments have the rule as being “three illegal moves”. Different rules apply to different tournaments.

The “touch move rule” may apply, requiring the player to move the same piece (if legally possible). If the touched piece cannot be legally moved, then any other legal move may be played for any other piece. If there are zero legal moves, then it must be either checkmate or stalemate!

In some cases, the position may have been illegal for many moves. If possible, the last legal position should be reconstructed and the game resumed from that point. Sometimes this is not possible and an official referee must make some adjustment, such as possibly restarting the entire game. Handling of these issues varies with the tournament rules.

In some tournaments, an illegal move is not undone at all, but can actually be claimed as a win immediately. This is usually possible only in tournaments where wins such as “capturing the King” are allowed as wins (e.g. lightning chess, 5-minute chess, etc.). Wins by “taking the King” are quite common in such tournaments. But wins by “illegal move claims” are very uncommon.

Related Chess Rules Topics

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